RESIDENCE AT SANTAREM 115 
from among its gigantic leaves. In the lakes, and 
among the tall grasses, were several small floating 
plants, chiefly cryptogamic, such as a Riccia, an 
Azolla, and a Salvinia ; but there was also a curious 
and beautiful E uphorbiad ( Phyllanthus fltdtans, sp. n. ), 
with two-ranked, roundish, heart-shaped leaves, of 
a pale green colour tinged with rose ; a fascicle of 
white radicles from the base of each leaf, and two 
to four small white flowers in each axil. Though 
wide as the poles asunder from the Salvinia, it was 
so like it in external aspect that I could hardly 
believe my eyes when. I found it to be a flowering 
plant. This is one out of many instances that have 
fallen under my notice of plants, widely different in 
the structure of their flowers and fruits, becoming 
assimilated in habit and in the form of their merely 
vegetative organs from being subjected to the 
same conditions of existence. That this is one 
cause, I cannot doubt ; but there are probably 
others, lying deeper than we have hitherto been 
able to penetrate, which, as in the analogous case 
of what has been styled mimicry" in insects, have 
aided in originating these startling and unexpected 
simulations. It was strange, also, to see great 
quantities of a floating Sensitive-plant, Neptunia 
oleracea, whose slender tubular stems were coated 
with cottony felt of an inch in thickness, as buoyant 
as cork, serving to sustain completely out of water 
the heads of pale yellow flowers, and the delicate 
bipinnate leaves, which shrank up at our approach. 
The same plant occurs here and there, in shallow 
waters, throughout the Amazon valley, and also 
on the western side of the Andes, on the borders 
of the Pacific ; and it reappears in China, where, 
